Dizziness can be caused by a problem in the nervous system or due to systemic causes. Within the nervous system, the problem can arise from the structures of the inner ear, the vestibulocochlear nerve, the brainstem, or the cerebellum. The inner ear and CN 8 are the peripheral components of this system, and the brainstem and cerebellum are the central components. Localizing the etiology of dizziness requires first determining whether the problem is neurologic or not, since dizziness can be caused by cardiovascular disease (e.g., arrhythmia, orthostatic hypotension), anemia, and endocrine dysfunction (e.g., hypoglycemia, thyroid disease) in addition to neurologic disorders. If dizziness is neurologic in etiology, one must determine whether the problem is peripheral (inner ear or CN 8) or central (brainstem/cerebellum). Medications can also cause dizziness through effects on the nervous system (e.g., antiepileptics), the inner ear (e.g., aminoglycoside toxicity), or the cardiovascular system (e.g., antihypertensives causing orthostatic hypotension).
The classic teaching is that the history in a dizzy patient should aid in classifying the symptom of dizziness as one of the following four entities:
Vertigo: a sensation of movement (spinning or tilting)—generally associated with a neurologic etiology
Light-headedness/presyncope: generally associated with a cardiovascular etiology
Dysequilibrium/imbalance: generally associated with a gait disorder (which may be neurologic or orthopedic, for example)
Other/nonspecific: generally associated with a psychogenic etiology
Although it is certainly important to elicit patients’ descriptions of their symptoms, research suggests that patients are inconsistent and imprecise in their descriptions of whether their dizziness is true room-spinning vertigo or not (Newman-Toker et al., 2007), and that patient descriptions do not necessarily correlate well with underlying etiology. An approach centered around timing, triggers, and associated symptoms correlates more closely with pathophysiologic etiology, and these elements of the history are more consistently and accurately reported by patients (Newman-Toker, 2007; Newman-Toker et al., 2007). Within this framework, dizziness is classified as acute or chronic, and chronic dizziness is classified as continuous or episodic. Episodic dizziness is then categorized based on whether the episodes are triggered or spontaneous (Fig. 12–4). If episodes are triggered, the trigger(s) must be elucidated (discussed further below).
Evaluation of Acute-Onset Continuous Vertigo
Acute-onset continuous vertigo is referred to as the acute vestibular syndrome. The differential diagnosis is essentially between posterior circulation stroke and vestibular neuritis (a presumed viral or postviral inflammation of the vestibular portion of CN 8). This is a paradigmatic example of a scenario in which peripheral and central etiologies of vertigo must be distinguished to determine whether dizziness is caused by a benign self-limited condition (vestibular neuritis) or a life-threatening condition (posterior circulation infarct). When obvious localizing findings are present (e.g., ataxia, eye movement abnormalities), the diagnosis of a central nervous system etiology is generally clear. However, many patients present with isolated vertigo, nausea, vomiting, and/or gait unsteadiness without obvious localizing findings on general neurologic examination. Moreover, MRI may be normal in the acute setting of posterior circulation infarction, so a normal MRI is not as reassuring as one would hope in an acutely vertiginous patient.
Fortunately, research has shown that a battery of three bedside tests is highly sensitive and specific for predicting posterior circulation stroke as the cause of acute continuous vertigo: the head impulse test, evaluation of the pattern of nystagmus, and the cover-uncover test for vertical skew deviation of the eyes (Kattah et al., 2009). This battery of tests was given the mnemonic HINTS (head impulse—nystagmus—test of skew) by the authors of the study. A concerning finding on any of these three tests (see below) should raise the index of suspicion for posterior circulation stroke as the cause of acute vertigo and warrants MRI, with repeat MRI after 24–48 hours if initial MRI is normal.
The head impulse test is a test of vestibular function. The examiner asks the patient to fixate on the examiner’s nose and maintain fixation while the examiner moves the head briskly to one side and then the other. Normally, the vestibulo-ocular reflex keeps the eyes fixated on the examiner’s nose, so when the head is moved to the right, the eyes instantly conjugately go to the left to maintain fixation; when the head is moved to the left, the eyes instantly conjugately go to the right to maintain fixation. If there is unilateral peripheral dysfunction (e.g., vestibular neuritis), when the head is turned to the abnormal side, the signal that the head has been turned cannot be transmitted to the central nervous system. As a result, the VOR fails and the eyes go with the head, requiring a catch-up saccade to come back to the nose.
For example, with left peripheral vestibular dysfunction, when the head is turned briskly by the examiner to the right (normal side), the eyes move appropriately instantly back to the left (normal response). When the head is moved briskly by the examiner to the left (abnormal side) there is no VOR, so the eyes also go to the left with the head and then make a catch-up saccade to the right back to the target. A catch-up saccade on the head impulse test to one side only is suggestive of peripheral vestibular dysfunction (inner ear or CN 8). In the setting of the acute vestibular syndrome, a normal head impulse test on both sides has been found to be predictive of stroke as the etiology. Note: the normal finding on this test is the concerning one in this context (i.e., concerning for stroke) since an abnormal head impulse test suggests a peripheral etiology in a patient with acute continuous vertigo.
With respect to nystagmus, the pattern concerning for a central etiology of the acute vestibular syndrome is direction-changing nystagmus. Direction-changing nystagmus refers to nystagmus in which the fast phase changes direction with changes in gaze direction: left-beating in left gaze and right-beating in right gaze. This suggests a problem with the gaze-holding mechanism, consistent with a central lesion (see “Direction-Changing Nystagmus Versus Nystagmus With the Fast Phase in the Same Direction in All Directions of Gaze” above).
Skew deviation is discussed in Chapter 11. Although it can occur with peripheral lesions, it is more commonly seen with central lesions. When vertical skew deviation of the eyes is evident in the acutely dizzy patient, a central etiology should be considered. When subtle, it may not be apparent, but can be elicited by the cover-uncover test. In this test, the examiner asks the patient to fixate on the examiner’s nose, and then the examiner moves one hand back and forth between the two eyes, looking for any vertical readjustment of each eye as it is uncovered. If vertical shifts of the eyes are seen with this test, this is considered a concerning finding for posterior circulation infarct as the cause of acute continuous vertigo.
A mnemonic for remembering the concerning findings in HINTS testing is provided in the study in which it is described: INFARCT: impulse normal, fast-phase (of nystagmus) alternating, refixation on cover-uncover test (Kattah et al., 2009). The presence of any of these three findings in a patient with the acute vestibular syndrome is highly predictive of stroke as the etiology.
It should be noted that this interpretation of this three-test battery is not the same in patients who are not acutely dizzy at the time of examination. Patients often present following an episode of dizziness when they are no longer dizzy. A normal head impulse test will be a normal finding in normal patients, and some patients may have a few beats of end-gaze nystagmus (which is direction-changing). Therefore, while the individual tests of the HINTS battery certainly have important utility in other contexts, the concerning findings in this battery suggest stroke only in a patient with acute-onset continuous vertigo.
Vertigo Accompanied by Acute Unilateral Hearing Loss
The presence of concurrent acute-onset vertigo and acute-onset unilateral hearing loss suggests a problem in the periphery (inner ear or CN 8) since hearing is represented bilaterally quite early in the brainstem auditory pathways and so is not easily disrupted by central lesions. Although most causes of peripheral vestibular lesions are benign, acute-onset unilateral hearing loss is a concerning finding: The inner ear can be infarcted by involvement of the internal auditory artery (also called the labyrinthine artery), which most commonly arises from the AICA. When the finding of acute hearing loss is added to HINTS (“HINTS plus”), the sensitivity for diagnosis of stroke as a cause of acute vertigo (and hearing loss) increases with slight decrease in specificity (Newman-Toker et al., 2013).
Vestibular neuritis is diagnosed on clinical grounds when there is acute-onset vertigo following a viral illness and examination findings are consistent with a unilateral peripheral etiology (nystagmus with fast phase in the same direction irrespective of the direction of gaze, abnormal head impulse test). Vestibular neuritis may be treated with a short course of steroids, although data about their efficacy in vestibular neuritis are limited. If symptoms are severe and persistent, a vestibular suppressant (e.g., meclizine) may be considered, but it should be emphasized to the patient that only a short course should be utilized since prolonged use may impair central compensation for peripheral dysfunction.
Hearing loss should not be present in pure vestibular neuritis. If hearing loss is present, the diagnosis of labyrinthitis should be considered. Labyrinthitis may also be postviral, but can be bacterial (e.g., due to meningitis or otitis media). Bacterial labyrinthitis requires antibiotic treatment.
Evaluation of Chronic Dizziness
For patients in whom dizziness is not acute and sustained, the goal of the history is to determine whether dizziness is episodic or continuous, and if episodic, if episodes of dizziness are provoked or unprovoked/spontaneous.
Continuous chronic dizziness can be due to:
Posterior fossa lesion (for example, tumor, Chiari malformation)
Medications (for example, antiepileptic, psychiatric, and cardiac medications)
In a patient who presents with episodic dizziness, one must first assess whether episodes of dizziness are unprovoked (i.e., spontaneous) or provoked. Spontaneous episodic dizziness may occur with:
When dizziness is provoked, specific triggers suggest particular underlying etiologies. Important triggers of episodic dizziness include:
Moving from supine to seated or seated to standing (suggesting orthostatic hypotension)
Changes in head position (suggesting benign paroxysmal positional vertigo; see below)
Exertion (suggesting cardiac etiology)
Sneezing/coughing/loud noises (suggesting perilymphatic fistula or superior canal dehiscence; see below)
Another feature of the clinical history that can be helpful is the length of episodes of vertigo:
Seconds to minutes: benign paroxysmal positional vertigo (See “Benign paroxysmal positional vertigo” below)
Minutes to hours: Ménière’s disease, transient ischemic attack (TIA), migraine
Episodic Dizziness Provoked by Positional Changes: Orthostasis and Benign Paroxysmal Positional Vertigo
Any patient who is already dizzy will likely feel that dizziness worsens with head position, as anyone who has been “sea sick” can confirm. The question here is whether the onset of dizziness is provoked by position change. Dizziness provoked by changes in body position (supine to seated or seated to standing) suggests orthostasis, and orthostatic vital signs should be obtained. Dizziness provoked by changes in head position (e.g., rolling over in bed) suggests benign paroxysmal positional vertigo.
Benign paroxysmal positional vertigo—Benign paroxysmal positional vertigo (BPPV) is caused by irritation of a particular semicircular canal by an otolith. The most commonly affected semicircular canal is the posterior canal, although anterior and horizontal canal BPPV occur rarely. BPPV is diagnosed by the Dix-Hallpike test in which the patient looks over one shoulder in the seated position and is then rapidly placed in the supine position with the head supported in the examiner’s hands and tilted below the level of the examining table while still turned to the side. The test is repeated on each side. In classic BPPV of the posterior semicircular canal, when the head is turned toward the affected side, after a delay of several seconds, the patient will experience vertigo and a mixed upbeat rotatory nystagmus will emerge with the rotatory fast phase toward the ground and the up-beating component more prominent in the upper eye (Fig. 12–5).
Dix-Hallpike maneuver. With BPPV of the right posterior semicircular canal, when the patient’s head is turned over the right shoulder and the patient is brought into the supine position, upbeat-torsional nystagmus occurs with the rotatory component in the direction of the ground. Reproduced with permission from Ropper A, Samuels M, Klein J: Adams and Victor’s Principles of Neurology, 10th ed. New York: McGraw-Hill Education; 2014.
If the Dix-Hallpike maneuver elicits downbeat nystagmus that appears without delay, a central etiology should be considered and neuroimaging should be obtained.
Posterior semicircular canal BPPV can be treated at the bedside through the Epley maneuver (Fig. 12–6). This begins like the Dix-Hallpike maneuver (head back and turned toward the affected side; Fig. 12–6A). After 1 minute, the patient’s head is turned 90 degrees (now facing away from the affected side and still tilted below the level of the examining table; Fig. 12–6B) for 1 minute. Then the patient turns the body toward the head to lie on the side, which puts the head in the downward-facing position (Fig. 12–6C). After 1 minute, the patient returns to the seated position (now 90 degrees from the original seated position; Fig. 12–6D). It is common for the patient to feel a recurrence of vertigo when returning to the seated position, and nystagmus may reemerge in the direction opposite the direction observed during the Dix-Hallpike maneuver. If the symptoms are convincingly reproduced on one side only by the Dix-Hallpike maneuver but no nystagmus is observed, it is still reasonable to perform the Epley maneuver on that side since nystagmus may be quite subtle.
Epley maneuver. The stages of the Epley maneuver for a patient with right posterior semicircular canal BPPV (clockwise from A). See text for explanation. Reproduced with permission from Ropper A, Samuels M, Klein J: Adams and Victor’s Principles of Neurology, 10th ed. New York: McGraw-Hill Education; 2014.
Anterior and horizontal canal BPPV are rare, and generally occur only as complications of the Epley maneuver for posterior canal BPPV such that the otolith that was originally in the posterior canal ends up in one of the other canals.
Anterior canal BPPV causes downbeat torsional nystagmus rotating toward the ceiling (away from the downward-facing ear) on Dix-Hallpike testing. However, as noted above, since downbeat nystagmus can be an indication of a central etiology of vertigo, and given the rarity of anterior canal BPPV, neuroimaging should be obtained if downbeat nystagmus is elicited. Since anterior canal BPPV is a rare condition, appropriate canal repositioning maneuvers for anterior canal BPPV are not well established.
Horizontal canal BPPV requires a different maneuver to be diagnosed: The patient is placed in the supine position and the head is rapidly rotated to one side and then the other, looking for pure horizontal nystagmus, which may be toward the ground (geotropic) or toward the ceiling (ageotropic), and may change position with the head on either side. The affected side is generally considered the side toward which the nystagmus appears more prominent when the nystagmus is geotropic, and the side to which it is less prominent with ageotropic nystagmus. Repositioning maneuvers to treat horizontal canal BPPV include the 360 roll maneuver (also called the Lempert maneuver) and the Gufoni maneuver.
In the Lempert (360 roll) maneuver, the patient begins in the supine position with the head turned such that the affected ear is down, then begins a series of 90-degree turns of the head—to looking at the ceiling, to looking to the side opposite the original side, to lying prone and looking down, to laying on the side of the affected ear (affected ear down), to supine, to seated (360 degrees). In the Gufoni maneuver, the patient goes from the seated position to laying on the unaffected side, then looking down (head turned over shoulder) while in that position, followed by returning to the seated position with the head still turned over the shoulder.
Episodic Dizziness Provoked by Loud Noises (Tulio’s Phenomenon) or Coughing/Sneezing: Perilymphatic Fistula and Superior Semicircular Canal Dehiscence
The symptom of dizziness triggered by loud noises (called the Tulio phenomenon), coughing, and/or sneezing is suggestive of two rare conditions of the inner ear: perilymphatic fistula and superior semicircular canal dehiscence. Perilymphatic fistula is a fistula between the middle ear and the inner ear, usually secondary to trauma. In superior semicircular canal dehiscence there is thinning of the temporal bone superior to the superior semicircular canal. In addition to the symptoms listed above, semicircular canal dehiscence can cause the symptom of autophony: patients report hearing their own heartbeat, chewing, and other internal sounds. Both conditions require imaging of the temporal bone and consultation with an otolaryngologist since surgical intervention may be indicated.
Unprovoked Episodic Dizziness
Ménière’s disease—Ménière’s disease is caused by idiopathic development of increased pressure in the inner ear (endolymphatic hydrops). The condition usually develops between early adulthood and late middle age (20s–50s). Episodes last hours and include vertigo, hearing loss, tinnitus, and a sensation of ear fullness. There may be progressive hearing loss and/or tinnitus between attacks. Patients may report sudden falls without loss of consciousness or vertigo, called otolithic crises of Tumarkin. The diagnosis is clinical, but audiometry may reveal fluctuations over time and/or progressive low-frequency hearing loss. Initial treatment includes low-salt diet and a diuretic. In refractory cases, labyrinthectomy or intratympanic gentamicin administration may be performed to ablate the inner ear.
Cogan’s syndrome causes Ménière-like attacks and interstitial keratitis. The syndrome can be seen in association with systemic vasculitis, or may occur in isolation.
Vestibular migraine—Dizziness is common in migraine, but some patients have severe vertigo as the prominent feature of their migraines (vestibular migraine). Nystagmus of any type may be observed during or between episodes in patients with vestibular migraine. Some patients may have episodic vertigo without accompanying headache, in which case the diagnosis of vestibular migraine is one of exclusion when no alternative explanation can be found after appropriate evaluation. Acute and preventive treatment of vestibular migraine is the same as for migraine in general (see “Treatment of Migraine” in Ch. 26), although meclizine, an antiemetic, or a benzodiazepine may be added to the acute abortive regimen for treatment of vertigo during acute migraines.
Posterior circulation transient ischemic attack (TIA)—Posterior circulation TIA should be considered in patients with episodic vertigo with vascular risk factors or history concerning for vertebral artery dissection (e.g., recent trauma) (see “Transient Ischemic Attack” in Ch. 19). In patients with recurrent episodes of vertigo concerning for posterior circulation TIAs, vascular imaging of the head and neck should be obtained to evaluate the vertebrobasilar system.
An important and life-threatening nonneurologic etiology of unprovoked episodic dizziness to consider is cardiac arrhythmia.